my 4 yr old boat has developed a half inch crack at the X , right on the coaming rim. the way i transport my kayak, it the coaming rests on the roof rack bars, and is tightened against them.
Should i try adding a strip of aluminum from underneath to span across the crack, held in with 2 pop rivets , or use the heat gun on it (maybe melting some copper wire mesh into the hot plastic)?
There are plastic welder kits that melt little heated “staples” into the plastic to stabilize a crack. Amazon has many of the kits as low as $21.99 with the gun and staples (just search for “plastic welder kit”). If you can get at the crack from behind, you could stabilize it without the melted plastic and staples being visible.
It can be welded to melt the pieces together, though you’re going to see the scar. More importantly, you should change the method of strapping the boat down to the rack if you don’t want this to continue to be a problem. A set of upright saddles or j-cradles will avoid putting stress on the rim (and a cockpit travel cover will keep the rain out, if that’s the concern).
I prefer to load my boats upside down too, on a set of Thule square bars. I have the bars spaced so all of the coamings on my hard shells fit between the bars rather than rest on them, which adds to security in transport since they can’t slide forward or back.
But on some occasions I have loaded other people’s boats with larger coamings hull up. Since I also transport a solo canoe I have in my car duffel bag of mounting straps and accessories a set of four of the hard foam pads that snap over the Thule bars to cushion the gunwales of the canoe when loaded, so I have popped those onto the rack when a coaming was going to rest on them.
Sidebar: The reason I have stuck with Thule rack systems over the 30-some years I have been hauling various boats is because (IMHO) the flat surface of the square bars tends to distribute the direct contact weight of loads on them better than round Yakima type or any of the “aero” bars. And I feel like attached accessories are more secure on a square base.
Isnt the coaming meant to be in contact with the roof bars? It is the stiffest part of the kayak and wont deform . When you tie down a kayak on its coaming ,you will be sure it wont loosen up during transport ( especially in the sun)
The coaming looks way over engineered to be just a support for a neoprene skirt band.
I agree with @PaddleDog52 and would never strap a boat down resting on the combing. It’s too narrow and the load is too concentrated. For rotomolded plastic boats I have suggested carrying them upside down to avoid oil canning the hull. A little oil canning on the deck, if it occurs, is cosmetic and will not affect how the boat handles. Carrying a rotomolded boat on its side with J-bars often works as well, as the sides are generally a bit stronger than the bottom of the hull.
Regardless of how the boat is carried, if possible have the supports centered on the internal bulkheads. Have the straps and tiedowns just snug, not too tight. Poly straps are very strong, don’t stretch, and generally don’t loosen up.
I also don’t recommend supporting the boat on unpadded narrow crossbars. Use saddles, J-bars, or at least foam blocks on the crossbars.to spread and cushion the load.
As others have said plastic boat repair is difficult and is beyond my experience. Good luck.
I can weld metals in a few methods. I tried plastic welding garbage can it didn’t last long. I’d plastic weld it and then get a strip of aluminum for underneath combing then pop rivet it with 4 large 1/4" flat head rivets. Rivet shaft is 1/8" or less.
Not sure if you use a skirt but you could file the rivets down a bit underneath. Them maybe a bead of silicone to protect the skirt or tape.